[abstract] EXPOSURE OF DIVERS TO UNDERWATER SOUND IN THE FREQUENCY RANGE FROM 800 TO 2250 Hz.

[abstract] EXPOSURE OF DIVERS TO UNDERWATER SOUND IN THE FREQUENCY RANGE FROM 800 TO 2250 Hz.

Author:

Parvin, SJ; Searle, SL; Gilbert, MJ

Abstract:

IINTRODUCTION: At high levels, underwater sound may cause startle and an aversion reaction. The tolerance limit to short duration underwater sound exposure is determined by the onset of non-auditory effects of the sound, such as dizziness, vibration and movement of the visual field. METHODS: Under controlled conditions, divers were exposed to underwater sound at levels of up to 191 dB re.1mPa. Physiological measurements, perceived loudness ratings and subjective comments were used to assess an acceptable noise exposure limit for recreational and military divers. The onset of non-auditory effects of the underwater sound was measured. RESULTS: Swimmers and recreational divers in warm water regions (bareheaded divers) will be able to hear incident underwater sound at levels above 67 dB re.1mPa. Bareheaded diver subjects experienced dizziness, vibration, and movement of the visual field at underwater sound levels above 170 dB re.1mPa. These effects subsided when the sound was removed. A foam neoprene diving hood provides significant (p less than 0.05) protection from incident waterborne sound over the frequency range from 500 to 16000 Hz. There is little correlation between the thickness of the hood and the sound protection that it provides. Wearing a suit and foam neoprene diving hood, divers were able to tolerate short duration underwater sound signals up to 191 dB re.1mPa. CONCLUSION: There was no evidence of temporary or permanent injury to divers exposed to short duration (64 x 4 second), underwater sound over the frequency range from 880 to 2250 Hz, and up to a maximum level of 191 dB re.1mPa. An acceptable exposure level for recreational divers is related to the potential for an aversion or startle reaction. At test frequencies from 880 to 2250 Hz, the acceptable level varies from 142 to 153 dB re.1mPa for bareheaded divers, and from 163 to 182 dB re.1mPa for divers wearing a diving suit and hood.